JP4484536B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device incorporated in a metal package by welding, and relates to a method for manufacturing a semiconductor device in which the internal space of the package is high vacuum.

  With reference to FIG. 5, a conventional semiconductor device device 100 will be described. FIG. 5 is a cross-sectional view of the semiconductor device.

  As shown in FIG. 5A, in the conventional semiconductor device 100, the support substrate 51 is made of metal, and the semiconductor element 52 is placed on the surface thereof.

  The semiconductor element 52 has a desired electric circuit formed on the surface thereof and is disposed near the center of the support substrate 51. The semiconductor element 52 and the external terminal 57 are electrically connected via the fine metal wire 56.

  The cap material 53 is made of metal and is provided on the surface of the support substrate 51 so as to cover the semiconductor element 52 and the fine metal wires 56.

  For example, when the internal space of the package is evacuated, a method of sealing the cap material 53 in a vacuum chamber is employed.

Therefore, the internal space is evacuated by providing a straw-shaped exhaust pipe 58 as shown in the figure (see, for example, Patent Document 1).
JP-A-9-126882

  As described above, in the case of a package that evacuates the internal space, outgassing during welding deteriorates the degree of vacuum. In particular, in a high-vacuum package, an adsorbent called a getter, which adsorbs gas inside the package, may be arranged in the package, but outgas from organic substances such as hydrocarbons cannot be adsorbed by the adsorbent.

  Further, since the support substrate and the cap material of the metal package are made of metal, they are generally sealed by welding the welding locations. This welding is generally resistance welding (projection welding, seam welding), laser welding, electron beam welding, or the like. The temperature at the time of these welding becomes about 1500 ° C., for example, and outgas is generated from organic substances used in the package in addition to hydrogen, nitrogen, and carbon dioxide generated by metal melting.

  In particular, since the welding area is a wide area over the entire circumference of the cap material, generation of outgas is a big problem.

  When outgas is further generated, the cap material and the metal of the support substrate also absorb this outgas. For this reason, the outgas is released again from the metal into the internal space over time, and the degree of vacuum also deteriorates.

  Therefore, in the prior art, all the outgas is discharged through the straw-shaped exhaust pipe 58 before shipment. That is, after the cap material 53 is welded, a method is adopted in which the package is left under a high vacuum and evacuated from the exhaust pipe 58 to close the exhaust pipe 58.

  Here, since the method of closing the exhaust pipe 58 is resistance welding performed simultaneously with the caulking of the cap material 53, it is difficult to perform this in the vacuum chamber, and the degree of vacuum is also reduced when closing the exhaust pipe 58. Deteriorate.

In other words, in the manufacturing process, the final vacuum degree is ensured by taking out gas and deterioration of the vacuum degree during resistance welding in advance, and specifically, it is necessary to perform evacuation of 10 ⁻⁹ Torr or more.

However, it takes about one week to leave the package in a high vacuum and perform evacuation at 10 ^-9 Torr or more, so there is a problem that cost performance is poor and unsuitable for mass production. .

  The present invention was made in view of such problems, and firstly, a semiconductor element manufacturing method for covering a semiconductor element fixed to a metal support substrate with a metal cap material and welding a welded portion over the entire circumference of the metal cap material, A first step of providing a minute air hole in the metal cap with respect to the welded part and welding the welded part, and deriving gas generated during welding from the air hole under a pressure lower than atmospheric pressure And a third step of welding the vent hole and setting the internal space sealed with the support substrate and the metal cap to a pressure lower than atmospheric pressure.

  Further, the vent hole is provided with a size of two-thirds or less of the thickness of the metal cap.

  Third, a semiconductor device manufacturing method of covering a semiconductor element fixed to a metal support substrate with a metal cap material and welding a welded portion over the entire circumference of the metal cap material, wherein the welded portion is partially attached to the welded portion. A first step of welding the welded portion with a minute ventilation hole, a second step of deriving gas generated during welding from the ventilation hole under a pressure lower than atmospheric pressure, and the ventilation hole. This is solved by including a third step of welding and setting the internal space sealed with the support substrate and the metal cap to a pressure lower than atmospheric pressure.

  The vent hole is welded by an electron beam or a laser.

  Further, the electron beam or laser is irradiated so that a focal radius of the electron beam or laser is 1.5 to 2 times the vent hole.

  In addition, the electron beam or laser is irradiated with a power density that melts the metal around the vent hole.

  In addition, the first to third steps are performed continuously under a pressure lower than the atmospheric pressure.

  In the present invention, the following effects can be obtained.

Outgas generated inside the package can be removed during welding sealing. Conventionally, the internal space has a degree of vacuum of about 10 ⁻¹ Torr to 10 ⁻² Torr (similar to atmospheric pressure) due to outgassing during welding, but in this embodiment, 10 ⁻³ Torr or more can be maintained. .

  Further, in the method of sucking out gas after welding with a straw-shaped vent hole, it was necessary to leave it in the vacuum chamber for about one week. However, in this embodiment, since it can be sucked in one to two days, it is possible to perform high vacuum. The package can be mass-produced.

  Furthermore, it is possible to evacuate and seal a product whose degree of vacuum has deteriorated during the manufacturing process.

  A specific structure of the semiconductor device 10 of the present invention will be described with reference to FIG. 1A is a plan view of the semiconductor device 10, and FIGS. 1B and 1C are perspective views of FIG.

  Referring to FIGS. 1A and 1B, a semiconductor device 10 of the present invention includes a semiconductor element, a case material, an adsorbent, a cap material, and an external terminal.

  Referring to FIGS. 1A and 1B, support substrate 11 is made of metal, and semiconductor element 16 is placed on the surface thereof. A plurality of pads 13 that are continuous with the external terminals 18 are formed in the periphery of the region where the semiconductor element 16 is placed. Here, the support substrate 11 has a circular shape, but may have another shape such as a rectangle.

  The semiconductor element 16 has a desired electric circuit formed on the surface thereof and is disposed near the center of the support substrate 11. The semiconductor element 16 and the pad 13 are electrically connected via the fine metal wire 15. The semiconductor element 16 is fixed by an insulating low-outgas die attach agent such as silicone resin, epoxy resin, or fluorine resin. Further, the semiconductor element 16 may be mechanically fixed to the support substrate 11 by a frame material as a fixing portion.

  The case material 12 is made of, for example, a metal such as Kovar, and is provided on the surface of the support substrate 11 so as to cover the periphery of the semiconductor element 16, the fine metal wire 15, and the pad 13. Further, the case material 12 includes a main body 12a that covers the semiconductor element on the side surface and the upper surface, and an opening portion 12b that is provided on the upper surface of the main body 12a and has a side wall 12c that is integrated with the upper surface. It is combined with the peripheral part of the substrate 11. Furthermore, materials other than metal can be used as the material of the case material 12, and glass, ceramic, resin material, or the like can also be used. The opening 12 b is located above the semiconductor element 16 fixed to the support substrate 11. In the figure, the support substrate 11 is exposed outside the case material 12, but the case material 12 may be provided with a ridge so as to cover this portion.

  The adsorbent 27 is disposed on the outer periphery of the case material opening 12b so as to overlap the case material 12. The adsorbent 27 has a protruding portion 27a on the inner periphery (inner diameter), and the protruding portion 27a is fixed in contact with the opening side wall 12c. That is, the adsorbing material 27 is fixed to the case material 12 by the protruding portion 27a incliningly contacting the clearance between the inner periphery of the protruding material 27a and the opening side wall 12c.

  The adsorbent 27 is formed of a sintered alloy of a metal (for example, zirconium, vanadium, titanium, etc.) having a characteristic of occluding impurities in the space in which the semiconductor element 16 is sealed, for example, hydrogen, oxygen, carbon dioxide, nitrogen, and the like. In the present specification, these are referred to as getters.

  The getter 27 is formed by, for example, forming a sintered alloy (getter material) of zirconium, titanium, iron, and vanadium into a ring shape with a thickness of about 0.1 mm to 0.2 mm, such as iron, copper, aluminum, or nichrome iron. It is fixed to the top and bottom of the fixed plate. Further, the getter material itself may be formed in a ring shape without using a fixed plate, or a two-layer structure in which the getter and the fixed plate are fixed by welding or the like, instead of a structure in which the fixed plate is sandwiched by the getter material, A combined multilayer structure may also be used.

  In the placement process, the getter 27 is inserted into the case material opening 12b while being weighted, and the protrusion 27a is bent. And since this becomes a stopper, there is substantially no clearance, whereby the getter 27 is fixed to the case material 12.

  Thus, since it can fix without using an organic solvent, the getter 27 can be fixed without generating the outgas which prevents a high vacuum state. Furthermore, fixing in a vacuum chamber where welding is impossible is possible.

  The external terminal 18 is made of a conductor fixed to the support substrate 11, passes through the support substrate 19, extends continuously from the pad 13, and has a function of performing electrical input / output with the outside. Therefore, the external terminal 18 is electrically connected to the semiconductor element 16 via the pad 13 and the fine metal wire 15. Further, the gap between the external terminal 18 and the support substrate 11 is filled with a filler 19 in order to prevent the outside air from entering the internal space. Furthermore, when the support substrate 11 is made of a metal, an electrical short circuit between the support substrate 11 and the external terminal 18 can be prevented by adopting an insulating material as the filler 19. More preferably, by employing low melting point glass as the filler 19, vaporization of the filler 19 due to high vacuum in the internal space can be suppressed. Further, the low melting point glass is excellent in workability because of its low melting point.

  The cap material 14 is, for example, a Kovar having a plate thickness of 0.2 mm, covers the case material 12 and the adsorbent material 27, is fixed to the support substrate 11 by welding or the like, and seals the semiconductor element 16. The portion of the cap material 14 corresponding to the upper side of the semiconductor element 16 is made of a glass material 20 that transmits light of a predetermined wavelength, and the glass material 20 has an antireflection film such as DLC (Diamond Like Carbon). Is coated.

The space sealed by the support substrate 11 and the cap material 14 has a pressure lower than the atmospheric pressure. Specifically, the atmospheric pressure in this internal space is an extremely low atmospheric pressure (high vacuum) of about 1 × 10 ⁻³ Torr.

  A method for manufacturing the semiconductor device 10 described above will be described with reference to FIGS. A method for manufacturing a semiconductor device 10 according to the present invention is a method for manufacturing a semiconductor device in which a semiconductor element fixed to a metal support substrate is covered with a metal cap, and a welded portion covering the entire circumference of the metal case is welded. A first step of welding a welded portion by providing a minute vent hole in the welded portion, a second step of deriving gas generated during welding from the venthole under a pressure lower than atmospheric pressure, and welding the venthole And a third step of setting the internal space sealed with the support substrate and the metal cap to a pressure lower than the atmospheric pressure.

First step (see FIGS. 1A and 1B)
First, the semiconductor element 16 is fixed to the support substrate 11. The semiconductor element 16 is fixed to the support substrate 11 with a low outgas die attach agent such as silicone resin, epoxy resin, or fluorine resin. Although not shown, a frame material may be fixed to the support substrate 11 by spot welding or soldering, and the semiconductor element 16 may be mechanically fixed by the frame material.

  A plurality of pads 13 made of a conductive material are formed on the support substrate 11 outside the semiconductor element 16 mounting region. Each pad 13 is electrically connected to an external terminal 18 extending outside the device by a metal thin wire 15 or the like. Thereafter, the case material 12 and the support substrate 11 are connected in the air or in an inert gas atmosphere.

  Next, the getter 27 is placed under a high vacuum such as in a vacuum chamber. The getter 27 has a ring shape that substantially matches the upper portion of the main body 12a of the case material and the opening side wall 12c.

In order to activate the surface of the getter 27 in the initial state, the getter 27 is preheated at about 500 ° C. to 800 ° C. with a heater or the like under high vacuum. When such getter activation (heating) is performed in an atmosphere containing oxygen, the getter burns, and thus it is necessary to carry out in a vacuum of 10 ⁻⁴ Torr or less.

  Although the heating temperature of the getter 27 differs depending on the alloy material constituting the getter 27, it is possible to take in oxygen in the atmosphere attached to the surface before assembly into the getter. The getter 27 is transported to the upper part of the case material 12, aligned, and placed on the outer periphery of the opening 12b.

  Then, as shown in FIG. 2, the cap material 14 is fixed while maintaining a high vacuum state, that is, in the same vacuum chamber. 2A is an external view of the cap material 14, and FIGS. 2B and 2C are external views of the semiconductor device 10 to which the cap material 14 is fixed.

  As shown in FIG. 2A, a vent hole 22 having a diameter of about 0.1 mm is previously formed in the cap member 14 by a laser or the like. Note that the vent hole 22 in this case is appropriately selected depending on the material and plate thickness of the cap material 14 because the periphery of the vent hole 22 is melted and closed by an electron beam in a later step. Specifically, the size (diameter) may be about one half of the plate thickness of the cap material. In the present embodiment, the cap material 14 is, for example, Kovar having a plate thickness of 0.2 mm, and the diameter of the vent hole 22 is about 0.1 mm.

  Then, as shown in FIG. 2B, the cap member 14 provided with the air holes 22 is disposed on the support substrate 11 in the same vacuum chamber. Thereby, the semiconductor element 16, the getter 27, and the case material 12 are covered with the cap material 14.

  And the welding location w with the support substrate 11 is welded over the perimeter of the cap material 14. This welding is resistance welding (projection welding, seam welding, etc.), laser welding, electron beam welding, or the like.

  In addition, as shown in FIG. 2C, the vent hole 22 is not provided in the cap material 14, but a portion of the welded portion w between the cap material 14 and the support substrate 11 may be left unwelded to form the vent hole 22. . In other words, the welded portion w between the cap material 14 and the support substrate 11 is left, for example, about 0.1 mm, which is used as the vent hole 22, and the other portions are welded.

  Second step (see FIG. 3): Thereafter, the package after welding is left under a pressure lower than atmospheric pressure. That is, it is left in the same vacuum chamber for about 1 to 2 days.

Thereby, the outgas generated in the package internal space by welding is led out from the vent hole to the outside. As described above, the pressure in the vacuum chamber is 10 ⁻⁵ Torr, and the pressure in the internal space can be set to about 10 ⁻³ Torr by leaving it in this for 1 to 2 days.

Third step (see FIG. 4): Thereafter, in a high vacuum of 10 ⁻⁴ Torr or more, that is, in the same vacuum chamber, the vent hole 22 is irradiated with an electron beam (or laser) L having a predetermined energy density, The ventilation hole 22 is welded. Since the vent hole has a diameter of about 0.1 mm, it can be said that it can be instantaneously welded and there is almost no outgas.

  Here, the energy density of the beam at the electron beam irradiation point can be obtained as a desired value by selecting the output according to the radius of the focusing point where the electron beam L is focused by the electromagnetic coil. Thus, the cap material 22 (and the support substrate 11) is irradiated with an output suitable for melting the metal (Kovar) surface. For example, if the beam is too weak, the metal surface cannot be melted. Conversely, if the beam is too strong, the metal evaporates at the irradiation point. Therefore, in the case of the present embodiment, the energy of the beam reaches about 1450 ° C. of the Kovar melting point, and an electron beam output of 0.3 to 0.5 mA is good.

  The diameter of the electron beam L is about 1.5 to 2 times the diameter of the vent hole 22. When irradiated over a wide range, the melted metal is supplied from the surroundings, so that the air holes 22 can be filled efficiently.

  Further, the irradiation with the electron beam L needs to be completed in a short time in order to suppress generation of excessive outgas. In this embodiment, the irradiation time is 0.02 sec. Welding is possible even at less than 0.02 sec or 0.02 sec or more, but it is preferable to make the time short as long as the air holes 22 are welded with a predetermined strength. When the vent hole 22 is provided in a part of the welding location w, the sealing can be performed in the same manner.

  Thereby, the support substrate and the metal cap are completely sealed, and a high vacuum in the internal space can be maintained.

For comparison, the device sensitivity was measured after the cap material 14 and the support substrate 11 were welded without providing the air holes 22 by the same manufacturing method as in the present embodiment. As a result, the measured value is reduced to about 50 to 60% of the initial value (the degree of vacuum in the vacuum chamber). When this is compared with the correlation data of the degree of vacuum and device sensitivity measured in advance, the vacuum in the internal space The degree was found to be about 10 ⁻¹ Torr to 10 ⁻² Torr (similar to atmospheric pressure).

On the other hand, according to the present embodiment, the device sensitivity is 100% of the initial value, that is, a vacuum degree of 10 ⁻³ Torr or more can be maintained.

  Further, according to the present embodiment, re-evacuation can be performed on a product whose degree of vacuum has deteriorated after completion.

That is, for products whose degree of vacuum has been found to be inspected after completion, vent holes 22 are provided again by laser irradiation or the like under high vacuum, and left in that state for one to two days to close the vent holes 22. Thus, the degree of vacuum can be 10 ⁻³ Torr or higher.

Moreover, long-term reliability cannot be guaranteed if the getter's adsorption effect is completely lost for products with a reduced degree of vacuum. In this case, an electrification heating type getter may be employed instead of the method of activation using an external heat source in the heater heating type getter 27 described above. That is, the electrode is attached to the nichrome iron which is the base material of the getter 27 and energized. According to this, heating work from the outside of the package becomes possible, so that the getter can be activated again at the time of re-evacuation of a product having a reduced degree of vacuum.

1A and 1B are a perspective view, a cross-sectional view, and a perspective view, illustrating a semiconductor device of the present invention. It is a perspective view (A)-(C) explaining the manufacturing method of the semiconductor device of this invention. It is a perspective view explaining the manufacturing method of the semiconductor device of this invention. It is a perspective view explaining the manufacturing method of the semiconductor device of this invention. It is a schematic diagram explaining the manufacturing method of the conventional semiconductor device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Semiconductor device 11 Support substrate 12 Case material 13 Pad 14 Cap material 15 Metal fine wire 16 Semiconductor element 17 Getter 18 External terminal 19 Filler 22 Vent 27 Getter 51 Support substrate 52 Semiconductor element 53 Metal package 54 Transmission window 55 Exhaust pipe w Welding location L Electron beam (laser)

Claims (3)

A semiconductor device in which a semiconductor element fixed to a metal support substrate is covered with a metal cap material, the metal cap material and the metal support substrate are welded, and the semiconductor element is disposed in a sealed space composed of the metal cap material and the metal support substrate. A device manufacturing method comprising:
Welding the welded spot in a state where a ventilation hole is provided in a part of the welded spot,
Deriving the gas generated at the time of welding from the vent hole under a pressure lower than atmospheric pressure,
The metal cap material corresponding to the vent hole and the periphery of the vent hole is irradiated with an electron beam or a laser with a diameter wider than the vent hole, and the metal of the metal cap material melted from the periphery of the vent hole is A method for manufacturing a semiconductor device, comprising: supplying to a vent hole to fill the vent hole.   The method for manufacturing a semiconductor device according to claim 1, wherein an adsorbent is provided in the sealed space. The method of manufacturing a semiconductor device according to claim 1, wherein the cap material is made of Kovar, and the cap material located above the semiconductor element is provided with a glass material.

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